Treating hydrocarbon charges by ultrafiltration is a process known in the art.
Japanese 4013509 describes the purification of oils such as lubricating oil or naphtha by filtering the oil through an ultrafiltration membrane made from polymers such as acrylonitrile styrene copolymer or polysulfone polymer. The oils treated can be lube oil, naphtha (e.g., residual oil from vacuum distillation), spent lube oil, or carbon-containing spent wash oil for engines. The process involves filtering the oil through an ultrafiltration membrane at a pressure of 1-20 kg/cm.sup.2, a flow rate of 2-4 m/sec and a temperature of 5.50.degree. C.
U.S. Pat. No. 4,411,790 describes the use of inorganic membranes for high temperature ultrafiltration of oils. The process can be used to regenerate used lube oil or to reduce the asphaltene content of heavy oils such as vacuum residua. The membrane is an inorganic ultrafiltration barrier having a pore radius of 50-250.ANG. coated with a metal oxide layer. The process is run at temperature above about 100.degree. C. Membrane plugging is prevented by periodically applying back pressure.
U.S. Pat. No. 4,797,200 describes separating heavy oil by diluting the oil with a solvent such as chloroform or toluene and ultrafiltering the diluted oil through an ultrafiltration membrane such as cellulose or polyvinylidene fluoride at about 750-1500 kPa and 20.degree.-125.degree. C. A permeate of reduced conradson carbon content and reduced vanadium and nickel content is recovered. The retentate can be fed to a deasphalting process. The permeate of reduced metal and conradson carbon residue content has the characteristics of gas oil and may be used as cat cracker feed with or without further hydrotreatment. The process can be run on raw or reduced crudes, heavy atmospheric and heavy vacuum residual oils, hydrorefined oils and hydrorefined atmospheric residual oils, shale oil, tar sands products, and coal liquefaction products.
U.S. Pat. No. 4,816,140 combines conventional deasphalting with membrane ultrafiltration. The solvent used to perform a conventional solvent deasphalting step is recovered from the deasphalted oil as filtrate by ultrafiltration through inorganic membrane.